The Democratic governor said in his veto message that the bill passed by the Republican-led Legislature would have placed "unnecessary burdens on public employees for the purpose of weakening labor organizations."

In addition to requiring annual consent for dues deductions, the legislation would have required a similar annual approval from public employees to spend a portion of their union fees on political activities.

Republicans who supported the bill called it a "paycheck protection" measure that preserved the rights of individual employees.

But Nixon said the legislation would have unfairly targeted unions with requirements that are not imposed on other automatic paycheck deductions, such as for college savings accounts or retirement plans. Those withholdings are based on a one-time authorization that the employee can revoke at any time, the governor said.

"The bill targets a single group of employees and imposes on them an unnecessary and cumbersome process," Nixon said in his official veto statement.

He did not publicize the veto with a press conference, instead listing it at the bottom of a news release noting that he had signed eight other unrelated bills.

Overriding Nixon's veto would require a two-thirds vote of both the House and Senate. That appears unlikely, because some Republicans joined with Democrats in opposing the bill. The legislation had passed the House last month by an 85-69 vote - 24 votes shy of the threshold needed for an override during an upcoming September session.